While the function of the histones in chromosome structure is becoming increasingly clear, many questions remain about the nonhistone proteins (NHP). Quantitation of the number of NHP/nucleus indicates that those which are visible by electrophoresis are present at a frequency of 2 x 10 to the 5th power to 6 x 10 to the 6th power copies per nucleus and probably represent structural rather than regulatory proteins. Some of the most frequent NHP represent nuclear matrix and HnRNA associated proteins. We propose to isolate, characterize and determine the function of many of the major structural NHP of the nucleus and examine their relationship to chromosome structure and chromosome binding.